Patent GB-673886-A (GB)
Title: Improvements in the control of electric motor-driven periodically reversible machines
Inventor: WALKER THOMAS BRADLEY
IPC: H02P23/00
Filed: 1948-03-02
Abstract: 673,886. Control of motors. BRAITHWAITE & SON, ENGINEERS, Ltd., I. March 31, 1949. [March 2, 1948] No. 6509/48. Class 38 (iii). Relates to the control of electric motor-driven periodically reversible machines of the type in which an inner cylinder rotates in an outer casing, a striker plate actuated by a motor-driven. shaft engaging a cam which is adapted to be rocked thereby to actuate a cam follower operating micro switches which through relays reverse the direction of rotation of the machine, means being provided for giving a time delay of variable duration between reversals. In Fig. 1, a pinion mounted on the shaft of the rotating cylinder of a washing machine meshes with a wheel to which is attached a striker plate D carrying plates d<SP>1</SP>, d<SP>2</SP>, and a cam face d<SP>2</SP>. A cam plate E carries a pin e<SP>1</SP> and cam faces e<SP>3</SP>, e<SP>3</SP>, e<SP>4</SP>. A cam follower F actuates switches W, X, through lever f<SP>2</SP>, and a cam follower H actuates switches Y, Z, through lever h<SP>2</SP>. The switch W (Fig. 5) operates forward and reverse contactors L, M, and has a third position forming the switch X. Switch Y provides automatic stopping of the machine in the normal unloading position, and switch Z operates a brake solenoid K which becomes effective in the "off" position. The machine is driven by an induction motor J from an A.C. supply 1, 2, 3, the relay circuit being energized from transformer T through rectifier V. When stopping the machine at its normal unloading position, or for normal reversal, the switch W is operated by the follower F being moved by cam face e3. In order to rotate the washing cylinder to a second unloading position, a push button S is closed to continue rotation until the follower F rises on to cam face e<SP>4</SP> thereby opening switch X and stopping the machine at the desired location. When switch q<SP>1</SP> is opened to stop the machine, switch Y allows continued movement until the cylinder has reached the correct unloading position. A time delay between reversals of the machine is introduced by means of a thermionic valve n<SP>3</SP> in order to allow deceleration. When relays u<SP>1</SP>, u<SP>2</SP>, which respectively control the contactors L, M, are not energized the valve load comprises resistor n<SP>1</SP>, and a condenser n<SP>2</SP> is charged. When either relay is energized by actuation of switch W, a relay U<SP>3</SP> is connected in the valve circuit but is not energized until the condenser discharges and removes a negative bias from the grid of the valve, whereupon the appropriate main contactor is closed. Resistors r<SP>1</SP>-r<SP>4</SP> are connectable across the condenser to allow for adjustable periods of delay. Means other than a thermionic valve may provide the delay period. When the machine is running the resistors r<SP>1</SP>-r<SP>4</SP> are short-circuited by switch O. A switch P prevents starting of the machine until the door is closed. Additional unloading positions may be afforded.